Wireless communication devices, such as wireless microphones, wireless audio transmitters, wireless audio receivers, and wireless earphones, include antennas for communicating radio frequency (RF) signals without the need for a physical cable. The RF signals can include digital or analog signals, such as modulated audio signals, data signals, and/or control signals. Wireless communication devices are used for many functions, including, for example, enabling broadcasters and other video programming networks to perform electronic news gathering activities at locations in the field and the broadcasting of live sports events. Wireless communication devices are also used by, for example, stage performers, singers, and/or actors in theaters, music venues, and film studios, and public speakers at conventions, corporate events, houses of worship, schools, and sporting events.
Wireless communications devices are often low profile and small so that the size of the devices is reduced for aesthetic reasons. It may also be desirable to place the antenna within the devices, instead of having the antenna on an exterior of the devices. The antennas included in devices can be designed to operate in one or more certain spectrum bands, and may be designed to cover either a discrete set of frequencies within the spectrum band or an entire range of frequencies in the band. For example, devices used in a conferencing environment may communicate using 2.4 GHz or 5 GHz Wi-Fi bands for sending and receiving various data and control signals. In addition, the polarization of antennas and their radiation pattern in wireless communications devices may vary as the orientation of the devices changes, e.g., when a user holds a device to their ear or places it on a table, etc.
Moreover, antenna design considerations can limit the number of antennas that are included within a single device (e.g., due to a lack of available space), while aesthetic design considerations can restrict the type of antennas that can be used. For example, whip antennas are traditionally good performers and by virtue of its external design, take up very little internal device space. However, these antennas can be expensive, distracting, and aesthetically unappealing, especially when they are long in length. As another example, certain devices may be physically small, which can limit the size of the ground plane for the antennas. For devices that need to communicate at several frequencies, typical antennas may not fit within the devices and/or may have poor efficiency.
Accordingly, there is an opportunity for antennas that address these concerns. More particularly, there is an opportunity for a multi-band slotted planar inverted F antenna (PIFA) that can be operated in multiple frequency bands, while being usable with electrically small ground planes that can fit within relatively small wireless communications devices.